232 



MOUNTING OP OBJECTS. 



cleanse the slides, of course answer equally well for cleansing 

 the hands. The most ready solvent for balsam is Ether ; but 

 the ordinary use of this being interdicted by its costliness, and 

 by the quickness with which it is dissipated by evaporation, 

 Alcohol or Oil of Turpentine may be used in its stead. 



131. Preservative Fluids. — Objects which would lose their cha- 

 I'acters in drying, can of course only be preserved in anything 

 like their original condition, by mounting in fluid ; and the 

 choice of the fluid to be employed in each case will depend upon 

 the character of the object, and the purpose aimed at in its pre- 

 servation. As specific directions will be given hereafter in re- 

 gard to most of the principal classes of Microscopic preparations, 

 little more will be required in this place, than an enumeration 

 of the preservative fluids, with a notice of their respective quali- 

 ties. For very minute and delicate Vegetable objects, especi- 

 ally those belonging to the orders Desmidiaceffi andDiatomaceas, 

 nothing seems to produce less alteration in the disposition ol 

 the endochrome, or serves better to preserve their color, than 

 Distilled Water ; provided that, by the complete exclusion of air, 

 the vital processes and decomposing changes can be alike sus- 

 pended. This method of mounting, however, is liable to the ob- 

 jection that confervoid growths sometimes make their appear- 

 ance in the preparation ; and it is preferable to make some 

 addition to the water, which shall be unfavorable to their de- 

 velopment. Saturation with eampJior, or shaking up with a few 

 drops of creasote, will sometimes answer ; but if the preservation 

 of color be not an object, nothing is better than the addition ot 

 about a tenth part of alcohol ; and where the loss of color would 

 be objectionable, the solution of a grain of bay-salt and a grain 

 of alum in an ounce of water will give it the requisite qualities. 

 For larger preparations of Algis, &c., what is called TJuvaites's 

 Fluid may be employed; this is prepared by adding to one 

 part of rectified spirit as many drops of creasote as will saturate 

 it, and then gradually mixing up with it in a mortar some 

 prepared chalk with 16 parts of water; an equal quantity of 

 water saturated with camphor is then to be added, and the mix- 

 ture, after standing for a few days, is to be carefully filtered. A 

 liquid of this kind also serves well for the preservation of many 

 animal preparations ; but it is said by Dr. Beale to become tur- 

 bid when thus employed in large quantity ; and he recommends 

 the following modification. Mix 3 drachms of creasote with 6 

 ounces of wood naphtha, and add in a mortar as much prepared 

 chalk as may be necessary to form a smooth thick paste ; water 

 must be gradually added to the extent of 64 ounces, a few lumps 

 of camphor thrown in, and the mixture allowed to stand for two or 

 three weeks in a lightly covered vessel, with occasional stirring ; 

 after which it should be filtered, and preserved in well-stopped 

 bottles. Of late years, Q-lycerine has been much employed as a pre- 

 servative fluid ; it allows the colors of vegetable substances to be 



